U.S. patent application number 14/346923 was filed with the patent office on 2014-08-28 for polishing composition.
This patent application is currently assigned to FUJIMI INCORPORATION. The applicant listed for this patent is FUJIMI INCORPORATION. Invention is credited to Yoshihiro Izawa, Yukinobu Yoshizaki.
Application Number | 20140242798 14/346923 |
Document ID | / |
Family ID | 47995758 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140242798 |
Kind Code |
A1 |
Izawa; Yoshihiro ; et
al. |
August 28, 2014 |
POLISHING COMPOSITION
Abstract
A polishing composition of the present invention is used for
polishing an object containing a phase-change alloy and is
characterized by containing an ionic additive. Examples of the
ionic additive include a cationic surfactant, an anionic
surfactant, an amphoteric surfactant, and a cationic water-soluble
polymer.
Inventors: |
Izawa; Yoshihiro;
(Kiyosu-shi, JP) ; Yoshizaki; Yukinobu;
(Kiyosu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIMI INCORPORATION |
Aichi |
|
JP |
|
|
Assignee: |
FUJIMI INCORPORATION
Kiyosu-shi, Aichi
JP
|
Family ID: |
47995758 |
Appl. No.: |
14/346923 |
Filed: |
September 28, 2012 |
PCT Filed: |
September 28, 2012 |
PCT NO: |
PCT/JP2012/075051 |
371 Date: |
March 24, 2014 |
Current U.S.
Class: |
438/693 ;
252/79.1; 526/272; 526/310; 526/312; 536/123.1; 536/56; 558/186;
558/27; 558/435; 562/45; 564/197; 564/282; 564/291 |
Current CPC
Class: |
H01L 45/16 20130101;
C09G 1/02 20130101; C09K 3/1445 20130101; C09K 3/1436 20130101;
C09K 3/1463 20130101; H01L 45/144 20130101; H01L 45/1666
20130101 |
Class at
Publication: |
438/693 ;
252/79.1; 558/27; 558/186; 562/45; 564/291; 564/282; 536/123.1;
558/435; 536/56; 564/197; 526/312; 526/272; 526/310 |
International
Class: |
C09G 1/02 20060101
C09G001/02; H01L 45/00 20060101 H01L045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2011 |
JP |
2011-218721 |
Claims
1. A polishing composition to be used for polishing an object
containing a phase-change alloy, wherein the polishing composition
contains an ionic additive.
2. The polishing composition according to claim 1, wherein the
ionic additive is one or more selected from the group consisting of
a cationic surfactant, an anionic surfactant, and an amphoteric
surfactant.
3. The polishing composition according to claim 1, wherein the
ionic additive is a cationic water-soluble polymer.
4. The polishing composition according to claim 1, wherein the
polishing composition contains the ionic additive in a
concentration of 0.0001 to 10% by mass.
5. The polishing composition according to claim 1, wherein the
phase-change alloy is a germanium-antimony-tellurium alloy.
6. A polishing method comprising: providing an object containing a
phase-change alloy; and using the polishing composition according
to claim 1 to polish a surface of the object.
7. A method for producing a phase-change device, comprising
polishing a surface of an object containing a phase-change alloy
with the polishing composition according to claim 1.
8. The polishing composition according to claim 2, wherein the
polishing composition contains the ionic additive in a
concentration of 0.0001 to 10% by mass.
9. The polishing composition according to claim 3, wherein the
polishing composition contains the ionic additive in a
concentration of 0.0001 to 10% by mass.
10. The polishing composition according to claim 2, wherein the
phase-change alloy is a germanium-antimony-tellurium alloy.
11. The polishing composition according to claim 3, wherein the
phase-change alloy is a germanium-antimony-tellurium alloy.
12. The polishing composition according to claim 4, wherein the
phase-change alloy is a germanium-antimony-tellurium alloy.
13. The polishing composition according to claim 8, wherein the
phase-change alloy is a germanium-antimony-tellurium alloy.
14. The polishing composition according to claim 9, wherein the
phase-change alloy is a germanium-antimony-tellurium alloy.
15. The polishing method according to claim 6, wherein the
phase-change alloy is a germanium-antimony-tellurium alloy.
16. The polishing method according to claim 14, wherein the ionic
additive is one or more selected from the group consisting of a
cationic surfactant, an anionic surfactant, and an amphoteric
surfactant.
17. The polishing method according to claim 14, wherein the ionic
additive is a cationic surfactant.
18. The method according to claim 7, wherein the phase-change alloy
is a germanium-antimony-tellurium alloy.
19. The method according to claim 17, wherein the ionic additive is
one or more selected from the group consisting of a cationic
surfactant, an anionic surfactant, and an amphoteric
surfactant.
20. The method according to claim 17, wherein the ionic additive is
a cationic surfactant.
Description
TECHNICAL FIELD
[0001] The present invention relates to a polishing composition
suitable for polishing an object containing a phase-change
alloy.
BACKGROUND ART
[0002] A phase-change material (PCM), which can be electrically
switched between an insulative amorphous phase and a conductive
crystalline phase, for an electronic memory application is utilized
for a PRAM (phase-change random access memory) device (also known
as an ovonic memory device or a PCRAM device). Examples of typical
phase-change materials suitable for this application include a
combination of an element of VIB group (chalcogenide, for example,
Te or Po) and VB group (for example, Sb) of the periodic table and
one or more metal elements such as In, Ge, Ga, Sn, and Ag. A
particularly useful phase-change material is a germanium
(Ge)-antimony (Sb)-tellurium (Te) alloy (GST alloy). The physical
conditions of these materials may reversibly change depending on
heating/cooling rate, temperature, and time. Examples of other
useful phase-change alloys include indium antimonite (InSb). The
memory information in the PRAM device is stored with minimizing
loss by the conduction characteristics of different physical phases
or states.
[0003] Chemical mechanical polishing (CMP) is known as a method for
polishing a metal-containing surface of a semiconductor substrate
(for example, integrated circuit). The polishing composition used
in CMP typically contains abrasive grains, an oxidizing agent, and
a complexing agent to effectively polish the surface by the etching
action.
[0004] CMP can be utilized for manufacturing a memory device that
uses a phase-change material. However, unlike a conventional metal
layer composed of a single component such as copper (Cu) and
tungsten (W), a plurality of elements such as sulfur (S), cerium
(Ce), germanium (Ge), antimony (Sb), tellurium (Te), silver (Ag),
indium (In), tin (Sn), and gallium (Ga) are mixed in a phase-change
material at a specific ratio that allows reversible phase-change
between a crystalline phase and an amorphous phase. For this
reason, the physical properties of many phase-change materials (for
example, GST) are different from the physical properties of
conventional metal layer materials, for example, in that they are
softer than other materials used in a PCM chip. Therefore, it is
difficult to apply the conventional polishing composition for
polishing metal-containing surfaces as it is to the polishing of a
phase-change material.
[0005] In such a situation, various investigations have been
performed on the polishing composition suitable for polishing an
object containing a phase-change alloy. For example, Patent
Documents 1 and 2 disclose a polishing composition for polishing an
object containing a phase-change alloy, the composition containing
abrasive grains, a complexing agent, water, and optionally an
oxidizing agent. The polishing compositions disclosed in these
documents are intended to improve conventional typical polishing
compositions used for polishing metal-containing surfaces thereby
to reduce a surface defect and a residue of a phase-change
material, but they have a problem that the etching rate of the
phase-change alloy is too high. In order to reduce the etching
rate, it is effective to reduce the concentration of the oxidizing
agent and complexing agent contributing to etching. However, if the
concentration of the oxidizing agent or complexing agent in the
polishing composition is reduced, a new problem occurs that the
amount of a polishing by-product or an organic residue adhering to
a polished object increases. It should be noted that the polishing
by-product includes polishing debris to be produced during
polishing, and that the organic residue refers to foreign matter
containing carbon derived from a polishing pad, a polishing
apparatus, a cleaning brush, or a polishing composition. The
polishing by-product and organic residue are also hereinafter
inclusively referred to as "defective foreign matter".
PRIOR ART DOCUMENTS
[0006] Patent Document 1: Japanese National Phase Laid-Open Patent
Publication No. 2010-534934 [0007] Patent Document 2: Japanese
Laid-Open Patent Publication No. 2009-525615
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0008] Accordingly, it is an objective of the present invention to
provide a polishing composition that can be suitably used for
polishing an object containing a phase-change alloy, particularly
to provide a polishing composition that can prevent occurrence of a
polishing by-product and an organic residue.
Means for Solving the Problems
[0009] To achieve the foregoing objective and in accordance with
one aspect of the present invention, a polishing composition to be
used for polishing an object containing a phase-change alloy, such
as a GST alloy, is provided that contains an ionic additive.
[0010] In one embodiment, the ionic additive is one or more
selected from the group consisting of a cationic surfactant, an
anionic surfactant, and an amphoteric surfactant.
[0011] The ionic additive is preferably a cationic water-soluble
polymer.
[0012] The polishing composition contains the ionic additive in a
concentration of preferably 0.0001 to 10% by mass.
[0013] Another aspect of the present invention provides a polishing
method for polishing a surface of an object containing a
phase-change alloy with the polishing composition according to the
above aspect.
[0014] Yet another aspect of the present invention provides a
method for producing a phase-change device that includes polishing
a surface of an object containing a phase-change alloy with the
polishing composition according to the above aspect.
Effects of the Invention
[0015] The present invention provides a polishing composition that
can be suitably used for polishing an object containing a
phase-change alloy, particularly a polishing composition that is
effective for the reduction of a polishing by-product and an
organic residue.
MODES FOR CARRYING OUT THE INVENTION
[0016] Hereinafter, one embodiment of the present invention will be
described.
[0017] A polishing composition according to the present embodiment
is used for polishing an object containing a phase-change alloy,
specifically polishing a surface of an object containing a phase
change-alloy to produce a phase-change device. The phase-change
alloy is utilized as a material that can be electrically switched
between an insulative amorphous phase and a conductive crystalline
phase for an electronic memory application in a PRAM (phase-change
random access memory) device (also known as an ovonic memory device
or a PCRAM device). Examples of the phase-change alloy suitable for
this application include a combination of an element of VIB group
(chalcogenide, for example, Te or Po) and VB group (for example,
Sb) of the periodic table and one or more metal elements such as
In, Ge, Ga, Sn, and Ag. A particularly useful phase-change material
is a germanium (Ge)-antimony (Sb)-tellurium (Te) alloy (GST
alloy).
(Ionic Additive)
[0018] The polishing composition of the present embodiment contains
an ionic additive. The ionic additive refers to a substance having
a positive or negative potential in an aqueous solution and being
capable of changing the potential, specifically the zeta potential,
of an object to be polished or defective foreign matter. It is
estimated that the ionic additive is bound or adsorbs to the
surface of both or either of a phase-change alloy and defective
foreign matter to thereby adjust the charges of the phase-change
alloy surface and the defective foreign matter surface to the same
sign (that is, both carry positive charges or negative charges),
and that a repulsive force to act between the phase-change alloy
surface and the defective foreign matter surface is thus caused.
That is, although details are unknown, the ionic additive is
estimated to act according to any of the following three cases.
[0019] (1) The ionic additive is bound or adheres to both the
phase-change alloy surface and the defective foreign matter surface
to cause a repulsive force between the phase-change alloy surface
and the defective foreign matter surface.
[0020] (2) The ionic additive is bound or adheres mainly to the
phase-change alloy surface to give a repulsive force to the
phase-change alloy surface acting against the charge that the
defective foreign matter originally has.
[0021] (3) The ionic additive is bound or adheres mainly to the
defective foreign matter to give a repulsive force to the defective
foreign matter acting against the charge that the phase-change
alloy originally has.
[0022] In the case where the ionic additive that adsorbs or adheres
to the phase-change alloy surface is selected to be used, the type
and the content of metals constituting the phase-change alloy are
preferably taken into consideration. That is, it is preferred to
select an ionic additive to be used that imparts larger amount of
charge per unit area to a metal contained at a higher content and
imparts less amount of charge per unit area to a metal contained at
a lower content, among the metals constituting the phase-change
alloy. For example, in the case of a GST alloy in which the ratio
of the mass of Ge, Sb, and Te is 2:2:5, it is preferred to select
an ionic additive to be used that imparts larger amount of charge
per unit area to Te, which is contained at a higher content, and
imparts less amount of charge per unit area to Ge and Sb, which are
contained at a lower content.
[0023] In the case where the ionic additive that adsorbs or adheres
to the defective foreign matter surface is selected to be used, the
components of the defective foreign matter are preferably taken
into consideration. For example, an organic residue derived from a
polishing pad made of polyurethane has a positive charge at the
vicinity of a pH of 3.0. An organic residue derived from a cleaning
brush made of polyvinyl alcohol has a negative charge at the
vicinity of a pH of 3.0. In the case where the components of an
organic residue as the defective foreign matter is known, if an
ionic additive having an opposite charge to the charge of the
organic residue is selected and used, an attraction force occurs
between the ionic additive and the organic residue, and the ionic
additive, in other words, the charge, can be efficiently imparted
to the organic residue surface. In the case where the defective
foreign matter is a polishing by-product, the type and the content
of metals constituting the phase-change alloy are preferably taken
into consideration as described above.
[0024] The ionic additive is a compound having a charge, and
specific examples thereof include a cationic surfactant, an anionic
surfactant, an amphoteric surfactant, and a water-soluble polymer
having a charge. Examples of the cationic surfactant include a
quaternary ammonium salt surfactant, an alkylamine salt surfactant,
and a pyridine ring compound surfactant. More specific examples
thereof include a tetramethylammonium salt, a tetrabutylammonium
salt, a dodecyl dimethyl benzyl ammonium salt, an alkyl trimethyl
ammonium salt, an alkyl dimethyl ammonium salt, an alkyl benzyl
dimethyl ammonium salt, a monoalkyl amine salt, a dialkyl amine
salt, a trialkyl amine salt, a fatty acid amidoamine, and an alkyl
pyridinium salt. Examples of the anionic surfactant include a
carboxylic acid surfactant, a sulfonic acid surfactant, a sulfate
surfactant, and a phosphate surfactant. More specific examples
thereof include coconut oil fatty acid sarcosine triethanolamine, a
coconut oil fatty acid methyltaurine salt an aliphatic
monocarboxylate, an alkylbenzene sulfonate, an alkane sulfonate, an
.alpha.-olefin sulfonate, a polyoxyethylene alkyl ether sulfate, an
alkyl sulfate, a polyoxyethylene alkyl ether phosphate, and an
alkyl phosphate. Examples of the amphoteric surfactant include an
alkyl betaine and an alkyl amine oxide. Specific examples of the
water-soluble polymer having a cationic charge include
polysaccharides such as chitosan and a cation-modified hydroxyethyl
cellulose, a polyalkylene imine, a polyalkylene polyamine, a
polyvinyl amine, a polyamine-epichlorohydrin condensate, a cationic
polyacrylamide, a poly(diallyldimethylammonium salt), and a
diallylamine salt-acrylamide polymer. Specific examples of the
water-soluble polymer having an anionic charge include a
polyacrylate, an ammonium salt of a styrene-maleic acid copolymer.
The repulsive force acting between the phase-change alloy surface
and the defective foreign matter surface increases as the absolute
value of the charge to be given is increased. It is preferred to
select the ionic additive from the point of view that polishing and
etching are not affected and the chemical or physical adsorbability
to the phase-change alloy and the defective foreign matter is high.
From such a point of view, when the phase-change alloy surface and
the defective foreign matter surface have a negative charge, a
cationic water-soluble polymer having many polar groups is
preferred, and in particular, a polyalkylene polyamine is more
preferred. Further, when the phase-change alloy surface and the
defective foreign matter surface have a positive charge, an anionic
surfactant or an anionic water-soluble polymer is preferred, and in
particular, a polyoxyethylene lauryl ether phosphate ester is more
preferred.
[0025] The molecular weight of the ionic additive is preferably
100,000 or less, more preferably 10,000 or less. The steric
hindrance of the ionic additive on the surface of the phase-change
alloy and the defective foreign matter decreases as the molecular
weight of the ionic additive decreases. As a result, the charge can
be efficiently imparted to cause the repulsive force to easily act,
and therefore the defective foreign matter is effectively
reduced.
[0026] The content of the ionic additive in the polishing
composition is preferably 0.001% by mass or more, more preferably
0.01% by mass or more. The probability that the ionic additive will
be bound or adsorb to the surface of the phase-change alloy and the
defective foreign matter increases as the content of the ionic
additive increases. As a result, the charge can be efficiently
imparted to cause the repulsive force to easily act, and therefore
the defective foreign matter is effectively reduced.
(Abrasive Grains)
[0027] The polishing composition may contain abrasive grains. The
abrasive grains may be any of inorganic particles, organic
particles, and organic-inorganic composite particles. Specific
examples of the inorganic particles include particles composed of
metal oxides, such as silica, alumina, ceria, and titania, silicon
nitride particles, silicon carbide particles, and boron nitride
particles. Specific examples of the organic particles include
poly(methyl methacrylate) (PMMA) particles. Among them, silica
particles are preferred, and particularly preferred is colloidal
silica.
[0028] The abrasive grains may be surface-modified. Since common
colloidal silica has a value of zeta potential of close to zero
under acidic conditions, the silica particles do not electrically
repel each other to easily cause aggregation under acidic
conditions. On the other hand, abrasive grains which are
surface-modified so that the zeta potential may have a relatively
large positive or negative value even under acidic conditions
strongly repel each other even under acidic conditions and are
satisfactorily dispersed. As a result, the storage stability of the
polishing composition is improved. Such surface-modified abrasive
grains can be obtained, for example, by mixing a metal such as
aluminum, titanium, and zirconium or an oxide thereof with abrasive
grains to allow the surface of the abrasive grains to be doped with
the metal or oxide thereof. Alternatively, the surface of the
abrasive grains may be modified with a sulfonic acid or a
phosphonic acid by using a silane coupling agent having an amino
group.
[0029] In any of the above cases, when the abrasive grains are
added, the potential possessed by the abrasive grains preferably
has the same sign as the potential possessed by the ionic additive.
When the charge possessed by the abrasive grains has the opposite
sign to the charge possessed by the ionic additive, the abrasive
grains may aggregate through the ionic additive.
[0030] The content of the abrasive grains in the polishing
composition is preferably 0.01% by mass or more, more preferably
0.05% by mass or more, further preferably 0.1% by mass or more. As
the content of the abrasive grains increases, there is an advantage
of increasing the removal rate of the phase-change alloy by the
polishing composition.
[0031] Further, the content of the abrasive grains in the polishing
composition is preferably 20% by mass or less, more preferably 15%
by mass or less, further preferably 10% by mass or less. As the
content of the abrasive grains decreases, the material cost of the
polishing composition is reduced, and the aggregation of the
abrasive grains is less likely to occur. Further, a polished
surface with few surface defects is easily obtained by polishing
the phase-change alloy with the polishing composition.
[0032] The average primary particle size of the abrasive grains is
preferably 5 nm or more, more preferably 7 nm or more, further
preferably 10 nm or more. As the average primary particle size of
the abrasive grains increases, there is an advantage of increasing
the removal rate of the phase-change alloy by the polishing
composition. The value of the average primary particle size of the
abrasive grains can be calculated, for example, based on the
specific surface area of the abrasive grains measured by the BET
method.
[0033] Further, the average primary particle size of the abrasive
grains is preferably 100 nm or less, more preferably 90 nm or less,
further preferably 80 nm or less. As the average primary particle
size of the abrasive grains decreases, a polished surface with few
surface defects is easily obtained by polishing the phase-change
alloy with the polishing composition.
[0034] The average secondary particle size of the abrasive grains
is preferably 150 nm or less, more preferably 120 nm or less,
further preferably 100 nm or less. The value of the average
secondary particle size of the abrasive grains can be measured, for
example, by a laser light scattering method.
[0035] The average degree of association of the abrasive grains,
which is a calculated value obtained by dividing the value of the
average secondary particle size of the abrasive grains by the value
of the average primary particle size thereof, is preferably 1.2 or
more, more preferably 1.5 or more. As the average degree of
association of the abrasive grains increases, there is an advantage
of increasing the removal rate of the phase-change alloy by the
polishing composition.
[0036] The average degree of association of the abrasive grains is
preferably 4 or less, more preferably 3 or less, further preferably
2 or less. As the average degree of association of the abrasive
grains decreases, a polished surface with few surface defects is
easily obtained by polishing the phase-change alloy with the
polishing composition.
(pH of Polishing Composition and pH Adjuster)
[0037] The pH of the polishing composition is preferably 7 or less,
more preferably 5 or less, further preferably 3 or less. As the pH
of the polishing composition decreases, the etching of the
phase-change alloy by the polishing composition is harder to occur,
and as a result, the occurrence of surface defects is further
suppressed.
[0038] A pH adjuster may be used for adjusting the pH of the
polishing composition to a desired value. The pH adjuster to be
used may be any of acid and alkali, and may be any of an inorganic
compound and an organic compound.
(Oxidizing Agent)
[0039] The polishing composition may contain an oxidizing agent.
The oxidizing agent has an action of oxidizing the surface of an
object to be polished. There is an effect of increasing the
polishing rate of the phase-change alloy by the polishing
composition when the oxidizing agent is added to the polishing
composition. However, when the phase-change alloy is polished with
a conventional typical polishing composition to be used for
polishing a metal-containing surface, the phase-change alloy tends
to be excessively polished. This is probably because the
characteristics of the phase-change alloy are different from the
characteristics of a metallic material such as copper commonly used
in a semiconductor device.
[0040] The content of the oxidizing agent in the polishing
composition is preferably 0.1% by mass or more, more preferably
0.3% by mass or more. The occurrence of an organic residue is
suppressed as the content of the oxidizing agent increases.
[0041] The content of the oxidizing agent in the polishing
composition is preferably 10% by mass or less, more preferably 5%
by mass or less. As the content of the oxidizing agent decreases,
excessive oxidation of the phase-change alloy by the oxidizing
agent is harder to occur. Therefore, excessive polishing of the
phase-change alloy is suppressed.
[0042] Examples of the oxidizing agent that can be used include
peroxides. Specific examples of the peroxides include hydrogen
peroxide, peracetic acid, percarbonates, urea peroxide, perchloric
acid, and persulfates, such as sodium persulfate, potassium
persulfate, and ammonium persulfate. Among them, persulfates and
hydrogen peroxide are preferred from the point of view of the
polishing rate, and hydrogen peroxide is particularly preferred
from the point of view of the stability in an aqueous solution and
the environmental load.
(Complexing Agent)
[0043] The polishing composition may contain a complexing agent.
The complexing agent has the effect of chemically etching the
surface of the phase-change alloy and thus increasing the polishing
rate of the phase-change alloy by the polishing composition.
However, when the phase-change alloy is polished with a
conventional typical polishing composition to be used for polishing
a metal-containing surface, excessive etching of the phase-change
alloy may occur, and as a result, the phase-change alloy tends to
be excessively polished. This is probably because the
characteristics of the phase-change alloy are different from the
characteristics of a metallic material such as copper commonly used
in a semiconductor device.
[0044] The content of the complexing agent in the polishing
composition is preferably 0.01% by mass or more, more preferably
0.1% by mass or more. Since the etching effect of the complexing
agent on the phase-change alloy increases as the content of the
complexing agent increases, the polishing rate of the phase-change
alloy by the polishing composition increases.
[0045] The content of the complexing agent in the polishing
composition is preferably 10% by mass or less, more preferably 1%
by mass or less. As the content of the complexing agent decreases,
excessive etching of the phase-change alloy by the complexing agent
is harder to occur. Therefore, excessive polishing of the
phase-change alloy is suppressed.
[0046] Examples of the complexing agent that can be used include
inorganic acids, organic acids, and amino acids. Specific examples
of the inorganic acids include sulfuric acid, nitric acid, boric
acid, carbonic acid, hypophosphorous acid, phosphorous acid, and
phosphoric acid. Specific examples of the organic acids include
formic acid, acetic acid, propionic acid, butyric acid, valeric
acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric
acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic
acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid,
benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic
acid, malonic acid, succinic acid, glutaric acid, adipic acid,
pimelic acid, maleic acid, phthalic acid, malic acid, tartaric
acid, citric acid, and lactic acid. Organic sulfonic acids, such as
methanesulfonic acid, ethanesulfonic acid, and isethionic acid, can
also be used. A salt, such as an ammonium salt and an alkali metal
salt, of an inorganic acid or an organic acid may be used instead
of an inorganic acid or an organic acid or in combination with an
inorganic acid or an organic acid. Specific examples of the amino
acids include glycine, .alpha.-alanine, .beta.-alanine,
N-methylglycine, N,N-dimethylglycine, 2-aminobutyric acid,
norvaline, valine, leucine, norleucine, isoleucine, phenylalanine,
proline, sarcosine, ornithine, lysine, taurine, serine, threonine,
homoserine, tyrosine, vicine, tricine, 3,5-diiodo-tyrosine,
.beta.-(3,4-dihydroxyphenyl)-alanine, thyroxine, 4-hydroxy-proline,
cysteine, methionine, ethionine, lanthionine, cystathionine,
cystine, cysteic acid, aspartic acid, glutamic acid,
S-(carboxymethyl)-cysteine, 4-aminobutyric acid, asparagine,
glutamine, azaserine, arginine, canavanine, citrulline,
.delta.-hydroxy-lysine, creatine, histidine, 1-methyl-histidine,
3-methyl-histidine, tryptophan, and iminodiacetic acid. Among them,
glycine, alanine, iminodiacetic acid, malic acid, tartaric acid,
citric acid, glycolic acid, and isethionic acid, or ammonium salts
or alkali metal salts thereof are preferred as a complexing agent
from the point of view of increasing the polishing rate.
(Metal Corrosion Inhibitor)
[0047] The polishing composition may contain a metal corrosion
inhibitor. When the metal corrosion inhibitor is added to the
polishing composition, there is an effect of further decreasing the
occurrence of surface defects such as dishing in the phase-change
alloy after polishing with the polishing composition. In addition,
when the polishing composition contains the oxidizing agent and/or
the complexing agent, the metal corrosion inhibitor relieves the
oxidation of the phase-change alloy surface by the oxidizing agent
and also reacts with metal ions, which are produced by the
oxidation of a metal of the phase-change alloy surface by the
oxidizing agent, to produce an insoluble complex. As a result, the
etching of the phase-change alloy by the complexing agent is
suppressed, and excessive polishing of the phase-change alloy is
suppressed.
[0048] Although the type of the metal corrosion inhibitor that can
be used is not particularly limited, a heterocyclic compound is
preferred. The number of members in heterocyclic rings in the
heterocyclic compound is not particularly limited. The heterocyclic
compound may be a monocyclic compound or a polycyclic compound
having a condensed ring.
[0049] Specific examples of the heterocyclic compound as a metal
corrosion inhibitor include nitrogen-containing heterocyclic
compounds, such as pyrrole compounds, pyrazole compounds, imidazole
compounds, triazole compounds, tetrazole compounds, pyridine
compounds, pyrazine compounds, pyridazine compounds, pyrimidine
compounds, indolizine compounds, indole compounds, isoindole
compounds, indazole compounds, purine compounds, quinolizine
compounds, quinoline compounds, isoquinoline compounds,
naphthyridine compounds, phthalazine compounds, quinoxaline
compounds, quinazoline compounds, cinnoline compounds, Buterizine
compounds, thiazole compounds, isothiazole compounds, oxazole
compounds, isoxazole compounds, and furazan compounds. Specific
examples of the pyrazole compounds include 1H-pyrazole,
4-nitro-3-pyrazole carboxylic acid, and 3,5-pyrazole carboxylic
acid. Specific examples of the imidazole compounds include
imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole,
1,2-dimethylpyrazol, 2-ethyl-4-methylimidazole,
2-isopropylimidazole, benzimidazole, 5,6-dimethylbenzimidazole,
2-aminobenzimidazole, 2-chlorobenzimidazole, and
2-methylbenzimidazole. Specific examples of the triazole compounds
include 1,2,3-triazole, 1,2,4-triazole, 1-methyl-1,2,4-triazole,
methyl-1H-1,2,4-triazole-3-carboxylate, 1,2,4-triazole-3-carboxylic
acid, 1,2,4-triazole-3-methyl carboxylate,
3-amino-1H-1,2,4-triazole, 3-amino-5-benzyl-4H-1,2,4-triazole,
3-amino-5-methyl-4H-1,2,4-triazole, 3-nitro-1,2,4-triazole,
3-bromo-5-nitro-1,2,4-triazole, 4-(1,2,4-triazol-1-yl)phenol,
4-amino-1,2,4-triazole, 4-amino-3,5-dipropyl-4H-1,2,4-triazole,
4-amino-3,5-dimethyl-4H-1,2,4-triazole,
4-amino-3,5-diheptyl-4H-1,2,4-triazole,
5-methyl-1,2,4-triazole-3,4-diamine, 1-hydroxybenzotriazole,
1-aminobenzotriazole, 1-carboxybenzotriazole,
5-chloro-1H-benzotriazole, 5-nitro-1H-benzotriazole,
5-carboxy-1H-benzotriazole, 5,6-dimethyl-1H-benzotriazole, and
1-(1'',2'-dicarboxy ethyl)benzotriazole. Specific examples of the
tetrazole compounds include 1H-tetrazole, 5-methyltetrazole,
5-aminotetrazole, and 5-phenyltetrazole. Specific examples of the
indole compounds include 1H-indole, 1-methyl-1H-indole,
2-methyl-1H-indole, 3-methyl-1H-indole, 4-methyl-1H-indole,
5-methyl-1H-indole, 6-methyl-1H-indole, and 7-methyl-1H-indole.
Specific examples of the indazole compounds include 1H-indazole and
5-amino-1H-indazole. Since these heterocyclic compounds have high
chemical or physical adsorbability to the phase-change alloy, they
form a stronger protective film on the phase-change alloy surface.
For this reason, excessive etching of the phase-change alloy after
polishing with the polishing composition is suppressed, and
excessive polishing of the phase-change alloy is suppressed.
[0050] The content of the metal corrosion inhibitor in the
polishing composition is preferably 0.001% by mass or more, more
preferably 0.01% by mass or more, further preferably 0.1% by mass
or more. As the content of the metal corrosion inhibitor increases,
excessive etching of the phase-change alloy after polishing with
the polishing composition is suppressed, and excessive polishing of
the phase-change alloy is suppressed.
[0051] The content of the metal corrosion inhibitor in the
polishing composition is preferably 10% by mass or less, more
preferably 5% by mass or less, further preferably 1% by mass or
less. As the content of the metal corrosion inhibitor decreases,
there is an effect of increasing the polishing rate of the
phase-change alloy by the polishing composition.
[0052] The present embodiment provides the following operation and
advantage.
[0053] The ionic additive contained in the polishing composition of
the present embodiment is bound or adsorbs to the surface of both
or either of a phase-change alloy contained in an object to be
polished and defective foreign matter to adjust the charge of the
phase-change alloy surface and the defective foreign matter surface
to the same sign (positive versus positive, or negative versus
negative) to thereby cause a repulsive force to act between the
phase-change alloy surface and the defective foreign matter
surface. For this reason, in the polishing of the object containing
the phase-change alloy, the polishing composition of the present
embodiment suppresses deposition and residue of defective foreign
matter produced from a pad, a polishing apparatus environment, and
the polishing composition on the object before or during
polishing.
[0054] The above embodiment may be modified as follows. [0055] The
polishing composition of the above embodiment may contain two or
more types of ionic additives. In this case, all the ionic
additives need not to have the same sign of potential as long as
the surfaces of the phase-change alloy in the object to be polished
and the defective foreign matter may carry the same sign of
potential as a result. [0056] The polishing composition of the
above embodiment may optionally further contain known additives
such as a surfactant, a water-soluble polymer, and a preservative
that are not classified into ionic additives. [0057] The polishing
composition of the above embodiment may be of a one-agent type or
may be of a multi-agent type, such as a two-agent type. [0058] The
polishing composition of the above embodiment may be prepared by
diluting a stock solution of the polishing composition with
water.
[0059] Next, examples of the present invention and comparative
examples will be described.
[0060] Polishing compositions of Examples 1 to 27 and Comparative
Examples 3 to 6 were prepared by mixing colloidal silica and an
ionic additive with water and adding an inorganic acid as a pH
adjuster to adjust the value of pH to about 3.0. Polishing
composition of Comparative Example 1 that does not contain an ionic
additive was prepared by mixing colloidal silica with water and
adding an inorganic acid as a pH adjuster to adjust the value of pH
to about 3.0. Polishing composition of Comparative Example 2 was
prepared by mixing colloidal silica and an oxidizing agent with
water and adding an inorganic acid as a pH adjuster to adjust the
value of pH to about 3.0. The details of the ionic additives in
each polishing composition are as shown in Table 1. Although not
shown in Table 1, the colloidal silica in each of the polishing
compositions of Examples 1 to 27 and Comparative Examples 1 to 6
had an average primary particle size of 35 nm and an average
secondary particle size of about 70 nm (an average degree of
association of 2), and the content of the colloidal silica in each
polishing composition was 0.5% by mass. Further, the polishing
composition of Comparative Example 2 contained 0.3% by mass of
hydrogen peroxide as an oxidizing agent.
TABLE-US-00001 TABLE 1 Ionic additive Content (% by Ionic
functional Type mass) group Comparative -- -- -- Example 1
Comparative -- -- -- Example 2 Example 1 Ammonium polyoxyethylene
styrenated phenyl ether 0.1 O.sup.- sulfate Example 2 Ammonium
polyoxyethylene allyl phenyl ether sulfate 0.1 O.sup.- Example 3
Ammonium polyoxyethylene lauryl ether sulfate 0.1 O.sup.- Example 4
Polyoxyethylene lauryl ether phosphate ester 0.1 O.sup.- Example 5
Linear alkylbenzenesulfonic acid 0.1 O.sup.- Example 6 Coconut oil
fatty acid sarcosine triethanolamine 0.1 O.sup.- Example 7 Coconut
oil fatty acid methyltaurine sodium 0.1 O.sup.- Example 8 Ammonium
polyacrylate 0.1 O.sup.- Example 9 Styrene-maleic acid copolymer
ammonium 0.1 O.sup.- Example 10 Lauryl dimethyl ethyl ammonium
ethyl sulfate 0.1 N.sup.+ Example 11 Stearyl dimethyl hydroxyethyl
ammonium p- 0.1 N.sup.+ toluenesulfonate Example 12 Lauryl
trimethylammonium chloride 0.1 N.sup.+ Example 13 Lauryl dimethyl
benzyl ammonium chloride 0.1 N.sup.+ Example 14 Lauryl dimethyl
benzyl ammonium chloride 0.1 N.sup.+ Example 15 Stearyl
dimethylaminopropyl amide 0.1 N.sup.+ Example 16 Chitosan 0.1
N.sup.+ Example 17 Dicyandiamide diethylenetetramine condensate 0.1
N.sup.+ Example 18 Polyvinyl amine 0.1 N.sup.+ Example 19
Polyamine-epichlorohydrin polycondensate 0.1 N.sup.+ Example 20
Cation-modified polyacrylamide 0.1 N.sup.+ Example 21
Poly(diallyldimethylammonium chloride) 0.1 N.sup.+ Example 22
Diallylamine hydrochloride-acrylamide polymer 0.1 N.sup.+ Example
23 Polyethylene imine (average molecular weight: 600) 0.1 N.sup.+
Example 24 Polyethylene imine (average molecular weight: 1,800) 0.1
N.sup.+ Example 25 Cation-modified hydroxyethyl cellulose 0.1
N.sup.+ Example 26 Cation-modified polyvinyl alcohol (average
molecular 0.1 N.sup.+ weight: 80,000) Example 27 Lauryl dimethyl
aminoacetic acid betaine 0.1 N.sup.+ Comparative Polyoxyethylene
nonyl propenyl phenyl ether 0.1 -- Example 3 Comparative Pullulan
0.1 -- Example 4 Comparative Polyvinyl pyrrolidone (average
molecular weight: 0.1 -- Example 5 50,000) Comparative Hydroxyethyl
cellulose (average molecular weight: 0.1 -- Example 6 25,000)
[0061] With respect to the ionic additives used in each of the
polishing compositions of Examples 1 to 27 and Comparative Examples
1 to 6, the charge on the surface of each metal of Ge, Sb, and Te
after treated with an aqueous solution of each of the ionic
additives (concentration: 0.1% by mass, pH: about 3.0) was measured
by the method and under the conditions shown in Table 2. The
results are each shown in "Ge", "Sb", and "Te" columns of the "zeta
potential" column of Table 4.
[0062] A blanket wafer containing a GST alloy (the mass ratio of
Ge, Sb, and Te is 2:2:5) was polished under the conditions shown in
Table 3 with each of the polishing compositions of Examples 1 to 27
and Comparative Examples 1 to 6.
[0063] A polishing by-product and an organic residue on each wafer
after polishing were determined. The determination of the polishing
by-product and the organic residue was performed by measuring all
the defects on each wafer after polishing with a defect inspection
apparatus and specifying and counting the polishing by-product and
the organic residue among all the defects with a scanning electron
microscope (SEM). The results are shown in the "Polishing
by-product" column and the "Organic residue" column of the
"Evaluation" column of Table 4. In these evaluation results, "oo"
represents the case where each of the number of the polishing
by-product and the number of the organic residue is 500 or less;
"o" represents the case where each of these numbers is from 501 to
1,000; ".DELTA." represents the case where each of these numbers is
from 1,001 to 10,000; and "x" represents the case where each of
these numbers is more than 10,000.
[0064] The thicknesses of each wafer before polishing and the
thickness of the wafer after polishing for a predetermined period
of time under the conditions shown in Table 3 were determined from
the measurement of sheet resistance by the direct current
four-probe method, and the polishing rate was calculated by
dividing the difference between the thicknesses of the wafer before
polishing and after polishing by the polishing time. The results
are shown in the "Polishing rate" column of the "Evaluation" column
of Table 4, wherein "o" represents the case where the calculated
value of the polishing rate is 1,000 .ANG./min or less; ".DELTA."
represents the case where the calculated value is higher than 1,000
.ANG./min and 2,000 .ANG./min or less; and "x" represents the case
where the calculated value is higher than 2,000 .ANG./min.
TABLE-US-00002 TABLE 2 To 100 mL of a 0.1% by mass aqueous solution
of an ionic additive adjusted to a pH of 3.0 was added 1.0 g of a
powder of Ge, Sb, or Te, and the zeta potential of each powder was
measured. The movement speed of particles was measured by the
dynamic/electrophoretic light scattering method, and the zeta
potential was determined by the following Smoluchowski's formula.
Smoluchowski's formula: .zeta. = (4-.pi..eta.U)/.epsilon. (.zeta.:
zeta potential, .eta.: viscosity of solvent, U: electric mobility,
.epsilon.: dielectric constant)
TABLE-US-00003 TABLE 3 Polisher: One-side CMP polishing apparatus
Polishing pad: Polishing pad made of polyurethane Polishing
pressure: 0.8 psi (.apprxeq.55 hPa) Rotational speed of platen: 60
rpm Polishing composition: Used with continuously fed without being
circulated Rotational speed of carrier: 60 rpm
TABLE-US-00004 TABLE 4 Evaluation Zeta potential (mV) Polish- Aver-
ing by- Organic Polish- Ge Sb Te age product residue ing rate
Comparative -1 -7 -3 -3.7 x x .smallcircle. Example 1 Comparative
-- -- -- -- x x x Example 2 Example 1 -33 -60 -62 -51.7
.smallcircle. .smallcircle. .smallcircle. Example 2 -27 -32 -73
-44.0 .smallcircle. .smallcircle. .smallcircle. Example 3 -54 -43
-60 -52.3 .smallcircle. .smallcircle. .smallcircle. Example 4 -94
-70 -94 -86.0 .smallcircle..smallcircle. .smallcircle.
.smallcircle. Example 5 -48 -73 -78 -66.3 .smallcircle.
.smallcircle. .smallcircle. Example 6 -48 -43 -50 -47.0
.smallcircle. .smallcircle. .smallcircle. Example 7 -43 -52 -59
-51.3 .smallcircle. .smallcircle. .smallcircle. Example 8 -15 -32
-2 -16.3 .DELTA. .DELTA. .smallcircle. Example 9 -27 -34 -29 -30.0
.smallcircle. .smallcircle. .smallcircle. Example 10 45 30 41 38.7
.smallcircle..smallcircle. .smallcircle..smallcircle. .smallcircle.
Example 11 53 51 56 53.3 .smallcircle..smallcircle.
.smallcircle..smallcircle. .smallcircle. Example 12 63 68 54 61.7
.smallcircle..smallcircle. .smallcircle..smallcircle. .smallcircle.
Example 13 60 51 34 48.3 .smallcircle..smallcircle.
.smallcircle..smallcircle. .smallcircle. Example 14 54 53 55 54.0
.smallcircle..smallcircle. .smallcircle..smallcircle. .smallcircle.
Example 15 62 74 99 78.3 .smallcircle..smallcircle.
.smallcircle..smallcircle. .smallcircle. Example 16 53 53 55 53.7
.smallcircle..smallcircle. .smallcircle..smallcircle. .smallcircle.
Example 17 28 35 28 30.3 .smallcircle. .smallcircle..smallcircle.
.smallcircle. Example 18 36 68 0 34.7 .DELTA. .DELTA. .smallcircle.
Example 19 4 25 5 11.3 .smallcircle. .smallcircle. .smallcircle.
Example 20 9 8 5 7.3 .smallcircle. .smallcircle. .smallcircle.
Example 21 21 20 5 15.3 .smallcircle. .smallcircle. .smallcircle.
Example 22 19 54 15 29.3 .smallcircle. .smallcircle. .smallcircle.
Example 23 61 70 37 56.0 .smallcircle..smallcircle.
.smallcircle..smallcircle. .smallcircle. Example 24 5 36 5 15.3
.smallcircle. .smallcircle. .smallcircle. Example 25 4 36 30 23.3
.smallcircle..smallcircle. .smallcircle..smallcircle. .smallcircle.
Example 26 14 14 13 13.7 .smallcircle. .smallcircle. .smallcircle.
Example 27 27 20 13 20.0 .smallcircle. .smallcircle. .smallcircle.
Comparative 16 12 6 11.3 x x .smallcircle. Example 3 Comparative --
-- -- -- x x .smallcircle. Example 4 Comparative -- -- -- -- x x
.smallcircle. Example 5 Comparative -- -- -- -- x x .smallcircle.
Example 6
[0065] As shown in Table 4, it was verified that in the case where
the polishing compositions of Examples 1 to 27 were used, the
polishing by-product and the organic residue significantly
decreased compared with the case where the polishing compositions
of Comparative Examples 1 to 6, which do not contain ionic
additives, were used.
* * * * *